Can agglomerated tall buildings reduce carbon emissions compared to a low-rise urban sprawl?

Abstract The building sector is a significant source of greenhouse gas (GHG) emissions globally. A city’s urban form and building typology can influence and even determine what strategies are implemented for GHG reductions. An important consideration for new construction is whether agglomerated mixed-use high-rises have the potential to reduce overall carbon emissions relative to a sprawl of low-rise dwellings. This study aims to contribute to that discussion by carrying out a comparative environmental assessment of the Burj Khalifa, the tallest building in the world, and Al Hudaiba, a nearby low-rise neighborhood in Dubai, United Arab Emirates. The aim of this exercise is to identify takeaways that can inform sustainable building construction and housing typologies. A life-cycle framework is used to analyze the annual per capita CO 2 e emissions of both systems, where material production, construction, building use, and end-of-life phases are considered. A baseline scenario is established in which certain benefits an agglomerated system of tall buildings would provide are realized, including having buildings with longer service lives and reducing transportation demand. Baseline results show that the Burj Khalifa has 11%–37% lower annual per capita life-cycle emissions, depending on the assumed electricity grid mix. Despite the higher operation emissions, reductions are achieved due to the Burj Khalifa’s relatively lower embodied carbon and transportation emissions. Monte Carlo simulation (MCS) is used to assess some of the uncertainties associated with baseline assumptions in each building phase. The MCS reveals that the Burj Khalifa leads to 5%–66% less annual GHG emissions per capita across all emission distribution percentiles, again depending on the electricity generation mix. Meanwhile, a sensitivity analysis shows that life-cycle emissions are mostly dependent on the energy use intensities of both systems. Had the Burj Khalifa been built as a low-energy use building, it would have been more CO 2 e efficient than 95% of Al Hudaiba’s MSC realizations, with a mean difference of 4.3 tonnes CO 2 e person −1 yr −1 . Overall, our findings demonstrate that agglomerated tall building systems can reduce building life-cycle emissions when they are intentionally designed to do so, especially if paired with a cleaner grid mix.